Morphological, pomological, and biochemical evaluation of several superior walnut (Juglans regia L.) genotypes.

Identifying and selecting superior genotypes in different countries and regions is a valuable breeding method in walnuts. The present study evaluated 31 quantitative and qualitative traits of seven superior walnut genotypes comparable to 'Jamal', 'Lara', and 'Serr' cultivars. The comparisons followed IPGRI descriptions. We evaluated pomological traits in the superior genotypes for four consecutive years (2019, 2020, 2021, and 2022), observing high variations among the genotypes. The thickness of husk, fruit weight, nut weight, and nut length ranged between 2.47–4.08 mm, 42.26–58.38 g, 10.43–14.60 g, and 29.59–37.61 mm, respectively. Also, kernel weight, percentage, color, plumpness, and fillness ranged between 5.22–6.97 g, 40.18–54.75%, 1.33–2.67 (approximately light), 2.33 (medium)—3.00 (plump), and 4.78 (medium)—7.00 (good), respectively. Biochemical features in the kernels varied significantly among the genotypes, particularly in the case of oil content (62.26–70.08%), SFA (10.10–13.03%), MUFA (13.38–36.40%), and PUFA (52.05–74.40%). Furthermore, kernel protein content, total polyphenols, and antioxidant activity ranged between 16.79–21.61%, 58.78–95.06 mg GAE/g, and 0.15–0.22 EC50, respectively. The kernel percentage correlated significantly and negatively with the flowering type (r = −0.414) and nut weight (r = −0.467) but positively with DFO (r = 0.545), fruitfulness percentage (r = 0.471), kernel weight (r = 0.412), saturated fatty acid (r = 0.375), oil percentage (r = 0.472), and protein percentage (r = 0.422). These genotypes were superior due to closed-shell seal, light kernel color, ease of kernel removal from nuts, lateral bearing, high kernel percentage, and high nutritional value. The selected genotypes are the bearers of desirable genes for future walnut breeding programs. [ABSTRACT FROM AUTHOR]